A vehicle exhaust system includes various components that transmit exhaust gases generated by a combustion engine to an ambient outlet. One such exhaust component is a catalytic converter that includes an outer shell defining an internal cavity that receives a catalyst substrate. The catalyst substrate can be formed as a single piece or can be separated into multiple pieces which are referred to as “bricks.” Typically, the substrates are wrapped with an insulating material, e.g. an insulation mat, to reduce heat radiation to adjacent components in a vehicle underbody, and to retain or support the substrate in the shell.
During vehicle operation, sensors are often used to monitor certain catalytic converter characteristics. For example, the catalytic converter often includes an oxygen sensor. The oxygen sensor is attached to a sensor boss that is installed on the outer shell. In one known configuration, the sensor boss is attached to an outer shell that surrounds a pair of substrates received within the internal cavity.
Typically, the method for manufacturing this type of converter configuration includes measuring the substrates, weighing the mats, wrapping the mats around the substrates, and inserting the wrapped substrates into a cylindrical outer shell. The shell is then sized, such as by reducing a diameter of the shell, to a desired diameter based on the measured substrate and mat weight characteristics. Prior to the stuffing step, a hole is typically punched into the outer shell at a location between the substrates, and a sensor boss is attached to surround this hole after the sizing process is completed. Typically, the sensor boss is welded to the outer shell about the hole location.
In certain configurations, the outer shell has to be sized to two different diameters to compensate for component tolerance variation. For example, one end of the shell that surrounds one substrate may be required to be sized to a smaller diameter than an opposite end of the shell that surrounds the other substrate. Traditional sizing operations for this type of configuration provide a poor weld area around the sensor hole. The differing diameters can result in large gaps between the boss and the shell at discrete circumferential locations, which is undesirable.